If the file disappears immediately after launching the game, your antivirus is likely the culprit.
If you must download it manually, only use reputable sites like DLL-files.com to avoid malware. Download the .zip file and extract the steam_api.dll . If the file disappears immediately after launching the
If the problem persists, you can repair the Steam Library folder via . If you'd like, let me know: Are you using the official Steam version or a repack ? Have you already checked your antivirus history ? If the file disappears immediately after launching the